Alternative oxidase

AOX present in ETS of plants.
When complex 4 of ETS is blocked, the formation of ATP and HEAT occurs due to AOX.

1. JAI NARAIN VYAS UNIVERSITY, JODHPUR Alternative oxidase BOT 302 Submitted to- Dr. Bhana Ram Gadi Submitted by- Dinesh Mehra M.Sc 3 rd sem.

2. ROTENONE ANTIMYCIN A CYANIDE MALONATE Salicyl hydroxamic acid 4 4 2

3. AOX can be specifically inhibited by salicylhydroxamic acid (SHAM) and n‐propyl gallate. If complex iv is inhibited -- 1 ATP & HEAT form. If complex I and complex iv both inhibited– only HEAT form , no ATP synthesis.

4. The AOX exists in the inner mitochondrial membrane as a homodimer in which two 32 kDa monomers interact non-covalently to form a dimer. When the 2 monomers are noncovalently linked it is in reduced active form. when covalently linked, it is in its oxidised inactive form.

5. Activity of AOX is increased in following condition---- When ATP/ADP ratio is high. In cold condition (heat generate) Presence of α kito acids (pyruvate & glyoxylate) . Drought, temp. generation of O 2 , H 2 O 2 .

6. Aox has important roles to play in countering abiotic stress in plants ranging from drought,light ,& salinity to heavy metal stress. High expression of AOX induces enhanced salt tolerance capability in Medicago truncatula through regulation of ROS and protection of photosystem.

7. Plants responds to biotic stress by eliciting a salicyli c acid mediated hypersensitive reaction to limit pathogen spread and in the process AOX expression is enhanced. Salicylic acid has been reported to inhibit mitochondrial ETC in tobacco cell cultures and this inhibition might be inducing AOX expression. AOX enhanced expressed causes lesions which causes programmed cell death.

8. Aox in higher plants is encoded by the nuclear genome . Aox was found to be encoded by a small family of nuclear genes such as AOX1,AOX2 The AOX 1 gene is widely known for its expression and it is present in both mono and dicotyledon plant species. On theother hand AOX 2 gene is ususally expressed in dicotyledon but absent in genome of all monocotyledon species examined to date.

9. References.. B uchanan Biochemistry-Molecular-Biology-of-Plants Alternative oxidase and plant stress tolerance , Bedabrata Sahaa , Gennadii Borovskiib , and Sanjib Kumar Pandaa https://www.youtube.com/watch?v=NhcSPjTdHyM